Selective Extraction of Palladium with Caffeine from Acidic Chloride Media

Abstract

In order to examine the possibility of caffeine as an extractant, the extraction of metal ions from acidic chloride media was studied at 298 K using the mixture solvent of chloroform and 2-ethyl-1-hexanol. Caffeine has exhibited a high selectivity for palladium(II) over base metals such as copper (II), nickel (II), and iron (III), and over precious metal such as platinum (IV). The stoichiometric relation in the extraction of palladium (II) with caffeine was elucidated by examining the effects of chloride ion, hydrogen. ion, and caffeine concentrations on its extractability. In addition, palladium (II) was found to be extracted selectively with caffeine from the mixture containing a 25-fold amount of platinum (IV) or copper (II). The stripping of palladium (II) was performed to an extent of 80% by a single batchwise treatment with an aqueous mixture solution of hydrochloric acid and thiourea.